I obtained a bucket of polar water from the Polar Ice Fields. I did a shop search and they're worth 2,000,000 sP! Why?

If you combine it with the Artificial Prism Chalice, you can make a Glacier Potion.

You can make a Glacier Potion when you combine it with the Artificial Prism Chalice from Millionaire Center at Asmodeus Genetech Lab in Darkside

Okay! I wonder if I should make a Glacier Potion myself....

There are some pretty cool glacier pets. If you don't want one, it depends on what the market is currently doing. Sometimes nobody is in the mood to make a Glacier pet and so the combined costs of the parts is more expensive than the Potion itself. The Bucket of Polar Water costs you nothing if you found going through the Fields a fun game that you would have done anyways, so making a GP may be worth any potential-loss to you. The ready-made potion does sell faster.